This invention relates to an apparatus for crossflow and mixing of solids which are at a different temperature to facilitate transfer of heat between the solids.
A common and recurring industrial need is that of transferring heat to or removing heat from materials for the purpose of, for example, preparing such materials for processing operations which are to be carried out at certain temperatures. After the processing, it is oftentimes desirable to bring the temperature of the material back to its previous temperature for stroage, packaging, etc.
Heat transfer or exchange between fluids is oftentimes accomplished by the well known process of placing two fluids of differing temperature in as close proximity as possible with each other, One of the simplest ways of doing this is to place a small pipe inside a larger pipe and then apply one fluid to the small pipe and the other fluid to the larger pipe (outside the smaller pipe). If the two fluids are applied to the pipe so that they both flow in the same direction (parallel flow), then the temperatures of the two fluids tend toward the average therebetween. If the fluids are applied to the pipes to flow in opposite directions (counterflow), then the temperature of each fluid tends toward the other fluid's entering temperature.
There have been a number of suggestions for providing heat exchange between solid materials including those disclosed in U.S. Pat. Nos. 2,592,783, 4,038,021, 4,182,400 and 4,207,943. In the first mentioned patent, heated or cooled balls are brought into direct contact with a material to be either heated or cooled inside a rotating drum. The balls are piled up in one end of the rotating drum and the material in the other end and the rotation of the drum tends to move the balls and material towards one another in a type of counterflow operation to somehow mix so that heat can be exchanged between the balls and the material.
The structure disclosed in the second mentioned patent includes an inclined tubular casing and an auger disposed within the casing, with the flights of the auger being perforated. A granular product to be dried, and heat conducting particles such as salt, are discharged into the casing from an opening in the bottom end of a tubular shaft of the auger. As the auger is rotated, the granular product and heat conducting particles are in some manner intermixed, with the granular product being forced upwardly in the casing since the product is of a size too large to pass through the holes in the auger flights, and the heat conducting particles apparently staying near the bottom of the casing since the particles are small enough to pass through the holes in the auger flights.
In the third mentioned patent, a counter-current heat transfer device is shown to include an inclined, rotatable, cylindrical drum in which is disposed a helical auger whose outer lip is maintained in contact with the interior wall of the drum. The auger includes a plurality of openings so that when a fine material is introduced into the upper end of the drum and a coarse material is introduced into the lower end of the drum, and the drum is rotated, the fine material sifts through the auger and the coarse material is carried by the auger to the upper end of the drum. In this manner, the coarse and fine material contact one another to exchange heat.
The fourth mentioned patent discloses a rotatable cylindrical drum which includes plates mounted on the interior surface thereof, and an elongate vibratory screen disposed within the drum but supported independently thereof. Vanes are located underneath the screen to guide material falling from the screen toward one end of the drum. A first granular material is introduced onto the screen at said one end of the drum, with the particles of this granular material being of a size greater than the size of the openings in the screen. A second granular material is introduced into the other end of the drum with the particle size of this material being less than the size of the screen openings. When the drum is rotated, the second granular material is carried from the bottom of the drum toward the top thereof where it then falls from the blades onto the screen. As the screen is vibrated, the first granular material is caused to move downwardly on the screen to contact the second material, and the second material is caused to sift through the apertures in the screen to be carried by the blades back up onto the screen. Heat transfer can thus take place between the first and second materials.
All of the above arrangements appear to provide for heat exchange between solids, but all are fairly complicated, requiring sophisticated equipment to implement.